Previous estimates that T. Rex weighed three to four tons were based only on the dinosaur's fossil bones, Hutchinson pointed out. But the new prediction involved over 30 different computer models.
"The method that we applied, creating a kind of computer sculpture of the body of a T. rex, takes into account the whole anatomy," he said.
Previous investigations into the biomechanics of dinosaurs have also often been based on living animals such as elephants, the research team added.
But the new research suggests T. rex walked very differently than the mammals, which use vertical, pillar-like legs. For the dinosaur to maintain its center of mass over its feet it would have needed to keep its legs bent, the team suggested.
The research team adds that its study has little bearing on the issue of whether T. rex was a scavenger or a predator.
It's a "false debate," with most experts now agreeing that the animal was both, Hutchinson said.
"If you look at living animals, pretty much anything that eats meat is both a predator and a scavenger," he added. "There's really no convincing evidence that says it was only a scavenger."
Paul Barrett is a dinosaur researcher at London's Natural History Museum who was not involved with the study. He says the new research does appear to undermine the idea of T. rex as a super-predator.
"It suggests that T. rex is basically a lot slower and more lumbering than a lot of the recent views on it have been," he commented.
However, "most of the animals that T. rex would have been hunting were also large and pretty slow moving and not particularly agile. So although it wouldn't have been a particular speedy predator, that might not have been a big disadvantage," Barrett said.
"Whether or not it was running after its prey at high speeds, it would still have been pretty awesome, I think." Hutchinson's team agrees, saying its weight and speed findings may also apply to other large dinosaurs such as Triceratops and Edmontosaurus, which T. rex is known to have eaten.
"These were also big clunky animals that clearly weren't running around at 50 miles [80 kilometers] an hour," Hutchinson said. "And why would [T. rex] need to turn quickly if it was preying on other big, relatively slow things?"
Smaller two-legged dinosaurs would probably have been able to outrun T. rex, however.
"T. rex probably didn't eat those, unless it got lucky and caught one off guard," Hutchinson said.
The environment during T. rex's day was also very different from today, Hutchinson added, and probably one where animals didn't need to be built for speed.
"I think there's a bias imposed by looking at living mammals in the Serengeti and elsewhere on open grasslands where they have a lot of space," he said.
"When T. rex lived there probably weren't a lot of huge open spaces to be charging around in at massive speeds."
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